Function start_api_server 

pub async fn start_api_server(
    addr: SocketAddr,
    api_key: Option<String>,
    server_port: u16,
    model_name: String,
    pid: u32,
    shutdown_rx: Receiver<bool>,
    host: String,
    tls_config: Option<RustlsConfig>,
    system_prompt_preset_name: String,
    web_search_engine: String,
    web_search_engine_url: String,
    web_search_enabled: bool,
    web_search_api_key: Option<String>,
    log_callback: Arc<Mutex<Option<Box<dyn Fn(String) + Send + Sync>>>>,
) -> Result<(), Box<dyn Error + Send + Sync>>